Overall asthma prevalence in U.S. adults also rose in 2013-2014

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Current asthma prevalence among obese women in the U.S. is almost double that of normal-weight women, but the same association was not seen in men, according to a CDC report.

Note that current asthma prevalence did not differ significantly by weight status for men.

Current asthma prevalence among obese women in the U.S. is almost double that of normal-weight women, but the same association was not seen in men, according to a CDC report.

In 2011–2014, obese women had a 14.6% prevalence for asthma versus 7.9% for normal-weight women and 9.1% for overweight women, reported Lara Akinbami, MD, of the National Center for Health Statistics (NCHS) in Atlanta, and colleagues.

Current asthma prevalence did not differ significantly by weight status for men, they wrote in an NCHS Data Brief.

They group analyzed 2001-2014 data from the National Health and Nutrition Examination Survey (NHANES) across all adult age groups, and found that obesity was significantly associated with higher asthma prevalence.

"This pattern was consistent across most demographic subgroups, except among men, for whom no statistically significant difference in current asthma prevalence by weight status was observed," they wrote.

While the current report bolsters findings from previous studies suggesting that obesity is a strong risk factor for asthma in adult women, but not men, the reasons for this are not clear, Akinbami told MedPage Today.

"Interestingly, asthma prevalence is higher in young boys than young girls, but this switches around the time of puberty. In adults, asthma prevalence is higher in women than men," she said.

It has been suggested that sex-related differences in fat distribution may at least partly explain the largely gender-specific asthma risk associated with obesity, and that hormones secreted by ectopic fat may contribute to asthma.

"My feeling is that it is the aggregation of a number of risk factors that contribute to the higher asthma risk among obese women," commented Erwin Gelfand, MD, of the National Jewish Health in Denver.

"Animal studies, and some human studies, have suggested that hormonal changes related to estrogen, leptin or other hormones may play a role in asthma," said Gelfand, who was not involved in the research.

Obesity was officially recognized as a major risk factor for asthma in adults by the American Thoracic Society in a 2010 report, which noted that obesity-related asthma is most likely a distinct phenotype of the chronic lung disease, characterized by increased severity and poor response to treatment.

Akinbami and colleagues found that from 2011 through 2014, the overall prevalence of asthma among adults in the U.S. was 8.8%, with 11.1% of obese adults, 7.8% of overweight adults, and 7.1% of normal-weight adults having asthma.

Also, obesity was associated with higher asthma prevalence rates among all age groups and racial groups.

Prevalence rates increased during this time period among overweight adults, but not among adults who were obese or whose weight was normal.

"That was not what we expected to see," Akinbami said. "Over the entire period, obese adults had the highest prevalence of asthma, but that prevalence rate did not increase."

The prevalence of current asthma among obese non-Hispanic whites was 10.9%, compared with 8.1% among normal-weight white adults, while the prevalence among non-Hispanic black adults who were obese was 13.6% compared with 6.6% in normal-weight blacks.

No significant differences in asthma prevalence rates were seen between normal-weight and overweight adults within any racial group.

For all age groups, current asthma prevalence was highest among adults with obesity, and no significant difference in asthma prevalence was seen between those in the normal weight and overweight categories.

"There was an increasing trend in asthma prevalence as weight increased that was observed most clearly in the 60 and over age group," the researchers wrote.

Akinbami noted that further research is needed to determine if weight loss is an effective treatment for asthma in patients who are also obese.

"We might be able to lower asthma rates by reducing obesity, but that is really an open question at this point," she said.

Akinbami and co-authors are employees of the CDC.

Reviewed by Robert Jasmer, MD Associate Clinical Professor of Medicine, University of California, San Francisco

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